1. Field of the Invention
This invention relates broadly in the field of electronic musical tone generators and in particular is concerned with the automatic detection of the chord type and root note played on a keyboard.
2. Description of the Prior Art
Musical chords can be defined as a combination of notes which sound "well" when played simultaneously. Chords are a set of notes with prescribed semi-tone intervals based upon a given tone which is called the root tone, or root note. If the root note is the lowest note of a chord the chord is said to be in the fundamental position, or normal order, or not inverted. If any note other than the root note is the lowest note then the chord is said to be "inverted" or in the inverted order. It is common practice to use inverted chords so that all the notes of a given chord are limited to a single octave of a keyboard musical instrument.
Because the selection and playing of chords requires both musical maturity and manual dexterity beyond the usual capabilities of a neophyte keyboard musical instrument player, a wide variety of aids have been developed so that the neophyte can play relatively advanced chordal harmonies with a minimum of skill.
Chord organs have been implemented in which the player selects the chord type and root note from a set of buttons much in the manner used for the bass accompaniment in accordians. In U.S. Pat. No. 2,645,968 Hanert discloses means to play chords selected from a set of buttons. The selected chord root and its musical fifth can be applied to a pedal tone generator by actuating one of two pedals.
Many of the current keyboard musical instruments of the organ family have provisions for semi-automatic modes for playing accompaniment chords and pedal tones. Some of these systems play the accompaniment in rhythmic patterns determined by the logic obtained from an automatic rhythm device. Moreover the pedal notes are altered in rhythmic patterns in which the selection of tones is transferred in a predetermined manner from the lower keyboard (left hand) and the rhythm timing is under control of a automatic device. In such systems for which the pedal note is determined from the accompaniment chords played on the lower keyboard, a detection subsystem is required to determine the proper root note for the actuated chords.
Various detection systems have been proposed and constructed for finding the root corresponding to a group of notes played on a particular keyboard. Many of these detection systems are very limited in that the player must preselect the kind of chords to be stored such as major and minor triads. Moreover some sort of default logic is required to take care of the almost nonsense situations in which incorrect or disonant note combinations are played on the lower keyboard (or any keyboard used to provide chord input data as a set of switches).
In U.S. Pat. No. 4,019,417 there is described a method for generating chords from notes actuated on a keyboard. A chord memory is provided which stores data for a preselected list of chord types. Logic is provided for "chord detection" based upon preselection of one or three note chord operation by the player. The chord detection logic determines whether the selected chord (one or three notes) is a "minor" or "major" chord. In addition, a root note is selected for the chord type decision. A priority logic is included which selects the root note of the lowest detected chord if more than one chord has been detected. Provision is also included for the case in which inverted chords are played on the input keyboard.
The prior art systems are primarily intended for begining players and limited in that the root note and chord type have to be given to the system. If the chord types are limited, then some simple root note and chord type selection has been accomplished such as in the system disclosed in U.S. Pat. No. 4,019,417. However, no provision has been made for more advanced players who can correctly play many chord types or for the transition skills between the beginner and expert player.
The present invention provides a novel means for detecting chord types and their root notes for a wide variety of chord types and incorporates features which permit operation even when either accidental mistakes or completely nonsense combinations of notes are played on the accompaniment keyboard.